Teschenit

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Teschenite is an ultramafic to mafic , relatively uniform-grain igneous rock with the composition of an alkaline gabbro or dolerite containing analcime .

Etymology and first description

Teschenitgang at the Red Rocks Gorge of the Murrumbidgee River in Southeast Australia

The word Teschenit is derived from its type locality of the city of Teschen , which is now divided into the Czech Český Těšín and the Polish Cieszyn . The rock was first scientifically described by Ludwig Hohenegger in 1861, but was still called Teschinite by him . Ferdinand Zirkel changed this in 1866 to the name in use today.

definition

According to the classification scheme of igneous rocks by Roger LeMaitre (2002), plutonic varieties of Teschenite would be classified as olivingabbro and volcanic varieties as picrit or picrobasalt . However, to maintain their independence, Gibb and Henderson (2006) define Teschenite as follows:

“Teschenites are medium to fine-grain igneous rocks consisting of plagioclase and clinopyroxene as well as subordinate analcime . Olivineschenite can contain up to 20 percent by volume of olivine . "

Occur

The mesocrats ( color number M '= 35 to 65), medium to coarse-grained, hypidiomorphic, dark green to black colored Teschenites occur, in addition to their plutonic appearance (as laccoliths ), predominantly hypabyssically as sub-volcanic dykes (dikes and bed dikes). Submarine extrusions with the formation of pillow lava , as well as lavas and pyroclastics are also known.

Petrology

Petrography

Teschenit from Poland

Teschenite has phenocrystals from 0.2 to 2 millimeter large olivine , up to 15 millimeter large, violet-brown, titanium-containing, occasionally zoned augite (with pyramidal sector zoning ), sometimes also diopside or aegirinaugite, up to 4.5 millimeters in size, tabular and sometimes arranged radially Plagioclase ( andesine to labradorite ), up to 6 millimeters in size, titanium-rich red-brown biotite tablets , 0.5 millimeters in size, gusset-filling analcime , iron-titanium oxides (1.0 to 2.5 millimeters in size titanomagnetite , magnetite and ilmenite ) and 0, Fluoroapatite needles 2 to 0.8 millimeters long .

The content of nepheline is low in contrast to Theralith . Brown kaersutite ( amphibole or hornblende ) or barkevikite (amphibole) can be added in corridors .

The base material contains alkali feldspars ( albite , sanidine , anorthoclase ), plagioclase, amphibole, biotite, analcime, apatite, titanite and / or iron-titanium oxides. It can be glassy or very rich in anal cimony. Secondary minerals are calcite , chlorite , epidote , goethite , very rare Hibschite (a hydro garnet ) and the zeolites natrolite , prehnite and fibrous Thomsonit .

Modally, Teschenites show roughly the following mineralogy:

  • Titanium Augite - 45 volume percent
  • Plagioclase - 30 percent by volume
  • Olivine - 10 to 15 percent by volume
  • Barkevikit - less than 5 percent by volume
  • Accessories : apatite (up to 1.2 percent by volume), ilmenite, pyrite , titanomagnetite

The structure of Teschenites is ophitic , subophitic or pegmatoid .

Varieties and synonyms

Distinctly olivine-accentuated varieties are called olivine-teschenite . Cuyamit is an olivine-free or low- olivine variety of Teschenite. Crinanite is medium-grained and the term is often used synonymously. Lugarite , named after the course of the Lugar Sill in Scotland, is another Teschenite variety, which is characterized by a predominance of titaniumugite and kaersutite phenocrystals, but contains little labradorite and analcime. Olivine is present. Bogusite is another synonym for Teschenite. At TheraLite approximate Teschenit is as theralitischer Teschenit (with anorthite -rich plagioclase), under increasing Alkalifeldspatgehalt with tendency toward Monzonite as Monzoteschenit and further to syenite as Syenoteschenit designated.

Geochemical composition

The following geochemical analyzes are intended to illustrate the composition of Teschenites:

Main elements

Oxide
wt.%		 Samtskhe
Georgia		 Guria
Georgia		 Shiant Isles Silesicum
28 analyzes		 Olivinteschenite
Poland		 Teschenit
Poland		 Syenoteschenit
12 analyzes		 Mallorca
6 analyzes		 Whangarei
New Zealand
SiO 2 46.82 49.46 43.01 41.42 39.74 43.44 43.13 43.94 45.08
TiO 2 1.69 1.30 1.48 2.66 3.88 3.26 2.47 3.01 2.56
Al 2 O 3 17.60 14.32 16.18 14.11 11.89 15.18 15.87 16.43 12.44
Fe 2 O 3 8.96 10.70 12.04 11.58 10.41 11.42 12.31 10.34 10.20
MgO 5.22 9.36 9.37 6.21 11.43 5.15 4.06 4.71 8.06
MnO 0.15 0.16 0.19 0.17 0.15 0.18 0.18 0.17 0.29
CaO 10.11 9.09 9.87 13.25 12.29 12.33 9.75 8.72 10.43
Na 2 O 4.22 3.78 2.38 2.75 3.74 3.17 3.63 3.42 3.53
K 2 O 4.15 1.46 0.20 2.08 1.66 2.76 2.75 3.75 0.80
P 2 O 5 1.12 0.36 0.12 0.71 0.54 0.67 1.09 0.85 0.52
S. 0.60 0.01 0.54 0.10

The appearance of feldspar representatives in Teschenites such as analcime or occasionally a little nepheline proves the nature of the rocks, which is undersaturated with silicon .

Trace elements

Trace elements
ppm		 Velvet cows Guria Shiant Isles Mallorca Bludovicze Punców Swietoszowka
Cr 14th 12 1674 15.2 7.1 420
V 243 144 305
Co 15th 39 72
Ni 15th 132 246 22.4 82 15th 239
Cu 140 76 152 27
Zn 69 69 87 84.2
Rb 45 14th 4.11 80.4 20th 87 26th
Sr 2152 890 1674 1177 778 2002 765
Zr 200 142 87 293 132 171 184
Ba 1680 264 46 938 366 1359 704
Pb 23 7th 1.23 7.8

Isotope ratios

Sr-Nd isotope diagram with the position of the Teschenites (green crosses, outlined with a yellow circle) in comparison to other European magmatites. The arrow marks the differentiation trend in the direction of the enrichment of 87 Sr / 86 Sr

The following isotope ratios were determined on Teschenites:

Isotope ratio Bludovicze Punców Swietoszowka
143 Nd / 144 Nd 0.51290 0.51287 0.51288
87 Sr / 86 Sr 0.70569 0.70425 0.70305
ε Nd 5.81 5.59 6.11
ε Sr 17.12 - 4.57 - 20.94

The existing Sr-Nd isotope ratios show relatively high and constant neodymium values (around +6 ), which approach the depleted DMM component (+10). Primitive end members are in or near the mantle array . Differentiated teschenites move away from the mantle array and develop towards high strontium ratios , which indicate contamination of the original mantle magma either through AFC processes (assimilation and fractional crystallization) or through metasomatic fluids. The more primitive members are related to the magmatites of the French massif Central , Cretaceous lamprophyren from the Pyrenees and the Ehrwaldites , which occupy a comparable position tectonically and chronologically. Magmatites from the Mecsek in Hungary ( Pannonian Basin ) show an almost identical development .

Conversions

Teschenites can be subject to strong transformation phenomena through hydrothermal metasomatosis such as chloritization , serpentinization , iddingsitization , saussuritization , carbonation , silification and zeolitization .

Occurrence

Table Cape in Tasmania, a Teschenite laccolith
Teschenit quarry near Rudów, Poland

The type locality forms part of a Teschenit-Pikrit association with countless smaller occurrences in the outer Carpathian arc ( Lower Skyskid flysch zone), which line up from northwestern Moravia to southern Poland. Their intrusion age is classified as 128 to 120 million years BP (Lower Cretaceous - Barremium to Aptium ), recently also somewhat younger with 122 to 110 million years BP (Aptium to Albium ).

Individual evidence

  1. ^ Hohenegger, L .: The geognostic conditions of the Northern Carpathians in Silesia and the adjacent parts of Moravia and Galicia . Perthes, Gotha 1861, p. 50 .
  2. ↑ Zirkel, F .: Textbook of Petrography . Vol. 2. Marcus, Bonn 1866, p. 635 .
  3. ^ Gibb, FGF and Henderson, CMB: Chemistry of the Shiant Isles main sill, NW Scotland, and wider implications for the perogenesis of mafic sills . In: Journal of Petrology . tape 47, 1 , 2006, pp. 191-230 .
  4. ↑ Harangi, S. et al .: Geochemistry and petrogenesis of Early Cretaceous alkaline igneous rocks in Central Europe: implications for a long-lived EAR-type mantle component beneath Europe . In: Acta Geologica Hungarica . Vol. 46/1, 2003, pp. 77-94 .
  5. ^ Wilshire, HG: The Prospect alkaline diabase-picrite intrusion, New South Wales, Australia . In: Journal of Petrology . tape 8 , 1967, p. 97-163 .
  6. ^ Stevens, NC: Igneous rocks of the Kalbar District, South-East Queensland . Vol. V Number 4. University of Queensland Press, Brisbane 1960, p. 1-10 .
  7. ^ Cochrane, N .: Geology of the Limestone Ridges District, Queensland . Pap. Dept. Geol. Univ. Qd., 1960.
  8. ^ Sutherland, FL et al .: An unusual Tasmanian Tertiary basalt sequence near Boat Harbor, Northwest Tasmania . In: Records of the Australian Museum . Vol. 48, 1996, pp. 131-161 .
  9. ↑ Žáček, V. et al .: The late Miocene Guacimal Pluton in the Cordillera de Tilarán, Costa Rica: its nature, age and petrogenesis . In: Journal of Geosciences . tape 56 , 2011, p. 51-79 , doi : 10.3190 / jgeosci.087 .
  10. ^ Patino, LC: Central America: Geology, Resources, Hazards, vol. 1 . Ed .: Bundschuh, J. and Alvarado, GE Taylor and Francis, London 2007, p. 549-654 .
  11. ↑ Lebedev, VA et al: Late Cenozoic volcanic activity in Western Georgia: evidence from new isotope geochronological data . In: Doklady Earth Sciences . Vol. 427 no. 5. Pleiades Publishing Ltd., 2009, p. 819-825 .
  12. ^ Paul, DK et al .: Petrology, geochemistry and paleomagnetism of the earliest magmatic rocks of Deccan Volcanic Province, Kutch, Northwest India . In: Lithos . 2007, p. 23 .
  13. ^ Lauder, WR: The geology of the Acheron Outlier (doctoral thesis) . University of Otago, 1953.
  14. ^ Hutton, CO: The Igneous rocks of the Brocken-Range-Ngahape area, Eastern Wellington . In: Trans. Roy. Soc. NZ 1943, p. 353-370 .
  15. ↑ a b Lucińska-Anczkiewicz, A. et al .: 40Ar / 39Ar dating of alkaline lamprophyres from the Polish Western Carpathians . In: Geol. Carpath. tape 53 , 2002, p. 45-52 .
  16. ↑ Enrique, P .: Las rocas básicas alcalinas intrusivas del Norte de Mallorca (Islas Baleares): características geoquímiquas . In: Geogaceta . tape 59 , 2016, p. 71-74 .